Spider mite cocoons ?
Chris Mycock writes, "The caterpillar (could it be a fox moth?) looks as if it has been parasitised by a wasp. The mature larvae, having eaten their fill, have munched their way out. Most have pupated - hence the fuzzy appearance - but two (top right and top centre on the caterpillar) look as if they have yet to complete their cocoons.See https://en.wikipedia.org/wiki/File:Macrothylacia_rubi_caterpillar_with_parasitoid_larvae_-_Niitv%C3%A4lja_bog.jpg"Fascinating! Many thanks to Chris. Jon